In recent years, increased environmental awareness has caused the practice of dumping untreated sewage, especially from marine vessels, into rivers, lakes and oceans to be outlawed with the goal of ending, or at least reducing, such practices. Regulations applicable to marine vessels operated in U.S. waters require that all vessels equipped with toilet facilities be equipped with an approved form of marine sanitation device (MSD) which can either hold the sewage until it can be discharged safely into a shore-side sewage handling facility or can treat it so that it can be safely discharged overboard, 33 CFR Chapter 1, Part 159.
Generally speaking, sewage treatment equipment for applications of this type falls into three rather broad categories (disregarding those devices which merely hold untreated sewage for shore-side disposal). These categories are (a) incineration of the sewage, (b) chemical treatment of the sewage, and (c) heating of the sewage to a temperature level which accomplishes the desired disinfection but which falls somewhat short of incineration. Clearly, the ultimate objective is to reduce the biological activity of the material to a level such that its discharge into waterways is safe as determined by tests defined in the regulations.
Unfortunately, the available types of MSDs which are capable of satisfying the requirements of these regulations are very expensive to buy, either as retrofit equipment for existing vessels or as new equipment on a new vessel, and are also difficult to operate and maintain. In addition, these MSDs generally use chemicals which are themselves dangerous or they use large amounts of the vessel's limited supply of electrical power. For these reasons, it is believed that owners of vessels commonly circumvent the regulations by not using the required equipment with the unfortunate result that the waterway pollution continues.